Effect of transcutaneous electrical nerve stimulation on the pressor response to static handgrip exercise

Background and Purpose. A proposed mechanism for the pain-relieving properties of transcutaneous electrical nerve stimulation (TENS) is gating of impulses carried by group III and IV afferent nerve fibers. The purpose of this study was to determine the effects of TENS on the presser response to static exercise, a response mediated by group III and IV muscle afferents. Subjects. Sixteen subjects (9 men, 7 women) with no known history of cardiovascular, neurologic, or musculoskeletal disease participated. Methods. Mie measured arterial pressure, heart rate, and sympathetic activity during sustained, 25% maximal handgrip exercise. Each subject performed the handgrip exercise with and without conventional TENS applied to the ipsilateral forearm and, in a separate trial, to the contralateral leg. Results. The sympathetically mediated presser response to handgrip exercise was blunted when TENS was applied to che ipsilateral forearm, but not when TENS was applied to the contralateral leg. Conclusion and Discussion. These data support the concept that central transmission of neural impulses traveling in group III and IV fibers can be modulated by other afferent inputs converging on the same spinal level.